lib/crypto: sha2: Add hmac_sha*_init_usingrawkey()

lib/crypto: sha2: Add hmac_sha*_init_usingrawkey()

While the HMAC library functions support both incremental and one-shot
computation and both prepared and raw keys, the combination of raw key
+ incremental was missing.  It turns out that several potential users of
the HMAC library functions (tpm2-sessions.c, smb2transport.c,
trusted_tpm1.c) want exactly that.

Therefore, add the missing functions hmac_sha*_init_usingrawkey().

Implement them in an optimized way that directly initializes the HMAC
context without a separate key preparation step.

Reimplement the one-shot raw key functions hmac_sha*_usingrawkey() on
top of the new functions, which makes them a bit more efficient.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250711215844.41715-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>